Dear Lifehacker,
I love trying out and using Android apps, but my phone warns me that it's "Low on space." How can that be, with 8 GB inside and a huge microSD card in place? How can I fix it?

Sincerely,
Desperately Seeking Droid Space.

Dear Desperately,

It's true—Android "storage" isn't easy to grasp, from the outset. Here's why you don't have as much room as you initially thought, and a few ways around your "cozy" allowance.

The Problem

On an iPhone, you rarely seem to run out of space for apps. You could, theoretically, but it doesn't seem like Apple enforces a hard limit on app installation and internal storage space. Note: This explanation is corrected from an earlier version.

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Android phones have internal storage built in, and also accept microSD cards, usually up to 32 GB in size. For the most part, the microSD is yours to do what you'd like with, although some apps will store folders and data on it. The solid memory chips that comprise your "internal storage," however, are used for both RAM in running active programs, and reserved in very specific ways for the main operating system, cache space, and then whatever is leftover for your "Internal phone storage"—where you can install applications.

How do you know how much space you have left for your continued app addiction? From your home screen, hit your Menu button, choose Settings, then select the "SD card & phone storage" section (which may have a slightly different name on certain phones). On this screen, you'll see two main sections: "SD card," which, as you guessed, provides the details on the card you've slid into this phone, and "Internal phone storage."

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After the space taken up by the main OS, the stock Google apps, and any apps that your phone carrier mandated, you're seeing what you've got left in the "Available space" section. You're seeing in the image here what I've got on my Nexus One, 27 MB—on a phone that has a total of 512 MB of internal storage. With the Nexus in particular, the phone that Google likely considered its strongest shot across the bow at the iPhone, this frustrating lack of app room was duly noted by many reviewers.

But the Nexus One is hardly alone in its small app capacity. Why the artificially fenced-off area for apps? The exact variances from phone to phone are due to hardware limitations (which are slowly improving with phones like the popular Droid Incredible), but the general restriction in app space is due to Google's need to maintain some kind of rights management on paid or restricted applications. Image via Wikimedia Commons.

Initially, to maintain a lock on which applications your phone can rightfully run, Google required that all applications be run from the phone's core internal memory, rather than on a card you could load into your needy friend's phone. That restriction is being lifted with the help of encryption tools, but in the meantime, the majority of apps haven't been crafted to run from an SD card, including Google's own apps. Which is a shame, because for the majority of users, the SD card isn't something that goes in and out every day—it's just an easily upgradeable bit of memory that hides underneath the battery, or in a side compartment.

The Solutions

If you're running out of space, and don't want to start sacrificing your apps to get more, you do have options. We'll start with the easier options and move on down to the tricky, geeky solutions.

Android 2.2: Move Bigger Apps to SD Storage

If your phone has picked up an Android 2.2 "Froyo" update, you have the ability to move some apps onto your SD card, freeing up internal storage.

To do so, head into Settings, choose the Applications menu, then pick "Manage applications" (or something similar). Switch over to the All tab, then hit your Menu button and choose "Sort by size." Now you can see the space hogs on your phone. You can't do anything (much) about some of the big hitters: Gmail, the Browser, and Maps, for example, will always be pretty big.

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But check out a few of your other apps. Start at the top and click down through them, and if you see a "Move to SD card" option, go ahead and hit it. There are drawbacks to this move, but they're few and uncommon. When your SD card is mounted for computer access, that app, if it's actively working, will likely close down, and it may not be able to run. And if your SD card is corrupted or lost, you'll lose access to that app—at least until you download it again, with your payment information backed up to Google.

Clear the Cache, and Maybe Data, on Some Apps

Over time, your Android applications stash away data that they plan to regularly have access to. The most temporary of this data, the app's cache, is used for storing things like Twitter profile pictures, lists of sites you've visited, and the like. Apps also store semi-permanent data, like your user account details and items you've chosen to download or keep handy.

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You can feel pretty safe wiping out the cache from an app, especially if it's taking up a sizable amount of space and you need just one ... more ... inch to install a new app—although the low space warnings won't go away anytime soon. Data, on the other hand, is something you won't want to wipe too often from apps you use all the time. Then again, we've read reports of apps like HTC's email client taking up 80 MB of data space on certain phones, so if your apps' data usage seems outsized, or you never use the app, go ahead and wipe.

Clear Out Apps You Don't Actually Use

Now that you know how to sort your applications by size, and understand the kind of space you're working with, this seemingly obvious advice takes on new importance.

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As I ran out of space on my own Android, I took the tack of trying to limit myself to only the apps I could fit on one homescreen. What apps did I really use every day? What apps did I think were essential, but in reality, I never actually clicked them? On my restricted app diet, I eliminated feature-rich PDF readers, apps my innate guilt though I should keep but never actually used (Mint.com, I'm looking at you), and leftover stuff I'd tested once, thought was cool, then never touched. Image via laihiu.

Android 2.2: Set Your SD Card as the Default Installation Location

If you've got a decently large microSD card in your phone, and you hardly ever take it out or mount it for file access, this next step might just work great for you—if you're willing to put in some geeky terminal work. Image via scriptingnews.

Root Your Phone and Set Up Apps2SD

When all else fails, the open-source, firmware-hacking community has your back, as they so often do. By rooting your phone, you'll have access to custom firmwares like CyanogenMOD, which allow you to enable Apps2SD and install any or all apps onto your SD card. At that point, your app space is limited only by what you can afford in storage from NewEgg. There are many warnings and caveats with rooting your phone, of course, and you shouldn't proceed unless you're sure of the process and what your particular risks are.

Hopefully we've been able to help you free up some space, Desperately, and helped other Android users running low on app storage figure out the path back to Market freedom. Here's hoping you can grab something good!

Love,
Lifehacker

P.S. — If we missed any other solutions to clearing out space for apps on an Android phone, do let us all know in the comments.